Molybdenum disulphide



United States Patent Claims priority, application Great Britain, Sept. 24, 1965,

6 Claims. (Cl. 252- 25) This invention relates to a novel molybdenum disulphide product of a particular physical form in which it possesses new and useful properties.

It is well known to grind molybdenum disulphide in air using, for example,'rotary or vibratory ball mills. The finely-divided molybdenum disulphide can be used either by itself as a dry, solid lubricant or in dispersions with lubricating properties.

According tothe invention, a novel molybdenum disulphide, with a surfacearea (as determined by nitrogen adsorption) of from 10 to 400 square metres per gram, is provided which is prepared by grinding the molybdenum disulphide in a low boiling point, low viscosity, low surface tension organic liquid. For convenience, the disulphide product prepared in this way will hereinafter be called oleophilic molybdenum disulphide to distinguish it from the untreated starting material. Oleophilic'f molybdenum disulphide has a considerable tendency to adsorb n-dotriacontane in preference to n-butanol (l), in contrast to the untreated starting material.

The molybdenum disulphide used may be either natural or artificial. One example of a natural molybdenum disulphide product is that supplied by Acheson Colloids, Dag 325."

Satisfactory products can be obtained by grinding in most organic liquids, but it is desirable to use one,.the bulk of which can be easily removed from theoleophilic 3,390,080 Patented June 25, 1968 "ice ing mill or device and it is desirable to continue the grinding until an oleophilic molybdenum disulphide having a surface area (as determined by nitrogen adsorption) of from 10 to 400, preferably from 30 to 200, square metres per gram is obtained. Usually this can be achieved by grinding at normal temperatures for the required period but the temperature of the mixture may be artificially increased if desired, for example, up to 400 C. In this case, liquids which have viscosities up to 600 centistokes at 100 F. (38 C.) may be used, for example, mineral lubricating oils, ranging from spindle oils to bright stocks.

One of the quickest and most effective techniques is I n to carry out the grinding in a vibratory ball mill.

molybdenum disulphide. Those liquids distilling below 500 C. and having a viscosity below-600 centistokes at 100 F. (38 C.) are therefore preferred. Liquids having a surface tension below 72 'dynes/cm, preferably from 10 to 40 dynes/cm., at 25 C. are preferred.

Suitable organic liquids are lower molecular weight hydrocarbons, including straight-chain or branched-chain, saturated or unsaturated alkyls, saturated or unsaturated, substituted or unsubstituted, cycloalkyls, and substituted or unsubstituted aromatic compounds. Examples of such compounds are n-heptane, octene-2, 2,2,4-trimethylpentane, cyclohexane, benzene or toluene. Branched alkyl compounds are particularly preferred. Other suitable organic liquids are those compounds which contain fluorine, chlorine, or phosphorus and chlorine, for example, carbon tetrachloride.

Other suitable organic liquids are the polar oxygen compounds such as isopropyl alcohol. Silicone fluids can also be used.

For best results, the amount of molybdenum disulphide in the molybdenum disulphide/organic liquid mixture (1) See notes at end of specification.

It is desirable to exclude air so far as possible during the grinding operation and this can be most easily achieved by filling the mill with the organic liquid first, followed by the balls and molybdenum disulphide. A suitable procedure is to fill the mill with the liquid, add half the balls, then the molybdenum disulphide and finally the rest of the balls.

When using a ball mill, it is of course desirable to use balls made of a material which does not react with the graphite and which does not wear unduly the grinding. Vibratory ball mills usually contain steel balls and these are suitable for the present purpose. It is preferred to use a hard grade of steel for the balls.

A magnetic filter can be used to remove small steel particles from the slurry. A circulatory system can also be used wherein the slurry is pumped through an internal magnetic filter and then returned to the mill.

A suitable vibratory ball mill is sold under the trade name Megapact (2), manufactured by Pilamec Limited. The grinding effect is produced by the impact of the balls upon the molybdenum disulphide and upon each other.

The slurry of olephilic molybdenum disulphide can be separated from the balls by seiving or by displacement by another liquid and sieving.

If a relatively high boiling organic liquid is used for grinding it is preferred to displace this liquid by a low boiling liquid. This liquid can then be removed by boiling. It is preferred to use vigorous boiling.

It is also possible to filter the slurry to obtain a filter cake of oleophilic molybdenum disulphide.

In either case it is preferred to remove the last traces of solvent by heating the filter cake in a vacuum oven for several hours, for example, at C. and at 1 mm.

mercury.

The following examples serve to illustrate the invention.

Example 1 Two oleophilic molybdenum disulphide products according to the invention were prepared from commercial disulphides. The table below compares the properties of commercial, non-oleophilic molybdenum disulphides.

It is thought that the proportions of surface area of the disulphide with polar sites or with non-polar sites are measured by the heats of adsorption of n-butanol or n-dotriacontane and that the ratios of heats of adsorption gives same measure of the ratios of polar" to non polar" sites.

(2) See notes at end of specification.

BET Surface Heat of Adsorp- Heat of Adsorp- Reierence No. Type of MOS: Area, metre tion of n-butanol tlon oi n-Cn in gram in milllcalorics/ mllllcalories/ gram gram Example A Commercial M081 A" ground in n-hept-ane for 4 40 384 396 hours (Megapacfl mill). Example B Commercial Mos; B" ground in n-heptane for 4 39 380 470 hours (Megapact). Comparison Commercial Mos; A ground in air for 4 hours 65 1,400 335 ("Megapact). I Comparison 2.. Commercial M08: "13 (as obtained from maker)- Comparison 3.. Commercial Mos; C (as obtained from maker). 8 42 9. 6 Comparison 4... Commercial M081 A ground by makers 22 281 110 The comparison samples 1 and 4 show some oleophilic properties, but they do, however, adsorb n-butanol to a large extent. Although the oleophilic molybdenum disulphides used in Examples A and B adsorb n-butanol they have very much higher ratios than do comparison samples land 4.

. The materials produced in Examples A and B can be used as thickeners of organic fluids, which form the base oils, to form dispersions or infusible greases. The greases show good mechanical stability. This use of the oleophilic molybdenum disulphide forms the subject of our copending U.S. patent application Se-r. No. 580,868 filed Sept. 21, ,1966; The oleophilic molybdenumdi sulphides can also be used as adsorbents for waxy components'of petroleum distillates and their dewaxing activity is rather more selective towards waxes than is the case with other molybdenum disulphides. This use of the oleophilic molybdenum disulphide forms the subject of our co-pending UK. patent application No. 33,531/65.

Example 2 It was found that the particle shape of oleophilic molybdenum disulphides was considerably different to the particle shape of air-ground molybdenum disulphides. Oleo philic molybdenum disulphides comprised thin, plate-like particles with major dimensions from 0.1 to 5 microns by from 0.1 to 5 microns and from 50 to 200 angstroms thick. On the other hand air-ground molybdenum disulphides comprised chunky particles with dimensions ranging from 0.1 x 0:1 x 0.1 micron to 0.5 x 0.5 x 0.5 micron.

NOTES (1) The heats of adsorption of n-dotriacontane and n-butauol on the molybdenum disulphide were measured using the Flow Microca'lori-meter as described in Chemistry and Industry, Mar. 20, 1965, 482-489.

(2) The Megapact mill contains grinding chambers which are steel cylinders of i k-inch interior diameter by 15 inches long and which are nearly filled with A inch diameter steel balls. The mill is fitted with a oneeighth horsepower electric motor and the oscillation can be adjusted from 1 to 5 mm. In operation, each cylinder was filled completely with the n-heptane and the steel balls and 25. to g-rams of molybdenum disulphide were added. This left from 15.0 to 200 cc. n-heptane in each cylinder. The. ends of the cylinders were then sealed by metal caps fitted with rubber washers and. the grinding carried out. After-grinding, the contents of the cylinders were placed in sieves which retained the balls -andthe n-heptane was removed from the oleop'hilic molybdenum disulphide by evaporation.

o I claim: g

' 1. An oleophilic molybdenum disulphide with a surface area of from 10 to 400 square metres per gram, prepared,

by grinding natural or synthetic molybdenum disulphide in organic liquid distilling below 500 C., having a viscosity below 600 centistokes at 38 C. and a surface ten"-- sion less than 72 degrees/cm. at 25 C.

2. A product as claimed in' claim 1, wherein the organic:

liquid has a surface tension from 10 to 40 dyues/cm. at 25 C. 7

3. A product as claimed in claim 1, wherein the grinding is carried out in a vibratory ball mill.

4. 'A product as claimed in clairn'l, wherein the amount of molybdenum disulphide in the molybdenum disulphide/organic liquid mixture does not'exceed 50% wt., based on the weight of mixture.

5. A product as claimed in claim 1, wherein the amount of molybdenum disulphide in the molybdenum disulphide/organic liquid mixture is from 2 to 20% wt.

6. A product as claimed in claim 1, wherein the'surface area of the molybdenum disulphide is firom 30 to 200 square metres per gram.

References Cited UNITED STATES PATENTS DANIEL E. WYMAN, Primary Examiner. I. VAUGHN, Assistant Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 ,390 ,080 June 25 1968 Aleksander Jerzy Groszek It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below:

Column 4 line 29 "72 degrees/cm. at 25 C" should read 72 dynes/cm. at 25 C Signed and sealed this 9th day of December 1969.

(SEAL) Attest:

Edward M. Fletcher, Ir. WILLIAM E. SCHUYLER,

Attesting Officer Commissioner of Patents 

1. AN OLEOPHILIC MOLYBDENUM DISULPHIDE WITH A SURFACE AREA OF FROM 10 TO 400 SQUARE METRES PER GRAM, PREPARED BY GRINDING NATURAL OR SYNTHETIC MOLYBDENUM DISULPHIDE IN ORGANIC LIQUID DISTILLING BELOW 500*C., HAVING A VISCOSITY BELOW 600 CENTISTOKES AT 38*C. AND A SURFACE TENSION LESS THAN 72 DEGREES/CM. AT 25*C. 